1. Field of the Invention
The present invention relates to the housing structure of an organic EL display device.
2. Description of the Related Art
As one of display devices, an organic EL display device (hereinafter referred to as OLED) has the following characteristics:
1. A display element constituting the OLED is a self light emitting element that does not require backlight.
2. Wide viewing angle and high visibility
3. The high response speed enables high-quality display without difference between moving images and static images.
4. Direct-current, low-voltage driving is enabled.
Therefore, the OLED is expected to contribute to applications for mobile/portable equipments having severe power requirements, and making television and notebook size personal computers thin and light in weight. In the present situation, since there are a small number of commercially available products provided with the OLED, the housing structures of OLEDs, including those that use resin frames for LCD panel, are classified as follows.
(1) Bonding the OLED to frames and fixing the upper and lower frames by circular dowels (spherical projections)
(2) Fixing resin frames for LCD to the OLED
Because of the structure that a display element constituting the OLED is a self light emitting element, since backlight in a liquid crystal display device (LCD) is not required, the OLED also does not require resin mold parts supporting the backlight structure, it has product advantages such as thin size, light weight, and low costs.
The method described in (1) has the following problem. That is, although double-faced tape is usually used for this kind of fixing, since sticking the double-faced tape to an OLED element requires adhesive or the like, the adhesive inevitably deteriorates with time, and there is a problem of reliability attributable to deterioration in the adhesive due to heat generation. In the fixing of the upper and lower frames, because of engagement assembly by circular dowels, both assembly precision and assembly rigidity are low because of slip in engagement portions of the dowels.
The method described in (2) also has the following problem. That is, although the rigidity of the element can be obtained by fixing to a resin mold, dies for manufacturing the resin mold are more expensive than those for metallic frames. To obtain higher rigidity by the resin mold, a display element becomes thicker as a whole, and its external size becomes larger, greatly reducing attraction of a product.
An OLED of the bottom emission method has the following problem. That is, the OLED of the bottom emission method has connection terminals of a flexible printed circuit substrate (FPC) and the like in the reverse side of the light emitting surface of a display element. Therefore, when the OLED has been placed in the housing, since flat cables of the FPC and the like, when connected to a driving circuit, are bent in the direction that peels the surface of flat cable bonding to the OLED, there is a problem in ensuring reliability.
However, since the OLED is structured to have no resin mold, there is a problem in impact resistance and torsion resistance. Therefore, to ensure the structure reliability of the OLED, a frame structure for maintaining the strength of the OLED is an indispensable factor.